Varecka L, Peterajová E, Sevcík J
Department of Biochemistry and Microbiology, Slovak University of Technology, Bratislava, Slovakia.
Gen Physiol Biophys. 1997 Dec;16(4):339-57.
The mechanism by which K+ inhibits vanadate-induced 45Ca2+ influx by human red blood cells (RBC) was studied using several independent approaches. The following results were found: 1. The inhibitory effect of K+ was absent when RBC were loaded with a Ca(2+)-chelator. This treatment at the same time inhibited the vanadate-induced K+ efflux, and the membrane hyperpolarization induced by Ca2+ in vanadate-treated cells. 2. The potency of K+, Rb+, and Cs+ to inhibit vanadate-induced Ca2+ influx corresponded to their ability to depolarize the RBC membrane via the Ca(2+)-activated K+ channel (K(Ca)). 3. Inhibition of the vanadate-induced 45Ca2+ influx by a protonophore proceeded in parallel with the inhibition of the vanadate-plus-Ca(2+)-induced membrane hyperpolarization. 4. Valinomycin in part released the inhibition of the vanadate-induced Ca2+ influx by known K(Ca) inhibitors (quinine, oligomycin, 4-aminopyridine) but not by inhibitors of the Ca2+ channel (Cu2+, HS-reagents, organic Ca2+ channel blockers). 5. K+ did not inhibit the vanadate-induced Ca2+ influx in dog RBC which have K(Ca) but no transmembrane K+ gradient. The inhibition of the vanadate-induced Ca2+ influx by external K+ appears to be due to the elimination of the electrical component of the Ca(2+)-motive force imposed by opening of the K(Ca). This implies that the Ca2+ carrier mediating the influx of Ca2+ in the presence of vanadate is of uniport type, and that the activity of K(Ca) may serve as a supporting element for Ca2+ influx.
采用几种独立的方法研究了钾离子抑制钒酸盐诱导的人红细胞（RBC）45钙离子内流的机制。发现以下结果：1. 当红细胞加载钙螯合剂时，钾离子的抑制作用消失。这种处理同时抑制了钒酸盐诱导的钾离子外流以及钒酸盐处理细胞中钙离子诱导的膜超极化。2. 钾离子、铷离子和铯离子抑制钒酸盐诱导的钙离子内流的效力与其通过钙激活钾通道（K（Ca））使红细胞膜去极化的能力相对应。3. 质子载体对钒酸盐诱导的45钙离子内流的抑制与对钒酸盐加钙离子诱导的膜超极化的抑制平行进行。4. 缬氨霉素部分解除了已知的K（Ca）抑制剂（奎宁、寡霉素、4-氨基吡啶）对钒酸盐诱导的钙离子内流的抑制，但未解除钙离子通道抑制剂（铜离子、硫氢试剂、有机钙离子通道阻滞剂）的抑制。5. 钾离子不抑制犬红细胞中钒酸盐诱导的钙离子内流，犬红细胞有K（Ca）但没有跨膜钾离子梯度。外部钾离子对钒酸盐诱导的钙离子内流的抑制似乎是由于消除了K（Ca）开放所施加的钙动力的电成分。这意味着在钒酸盐存在下介导钙离子内流的钙载体是单向转运体类型，并且K（Ca）的活性可能作为钙离子内流的支持因素。
